This invention relates to a multiport rotary valve for directing multiple fluid streams and, in particular to an improved rotary valve for simultaneously directing a plurality of fluid streams into and out of a fluid-solid contacting apparatus employed for separating a multi-component fluid mixture.
Continuous fluid-solid contacting systems have been used to effect a separation of a multicomponent fluid mixture into its components by employing the different affinities of the solid towards individual components of the fluid mixture. Typically, the fluid mixture in such a separation is brought into contact with a bed of solid. As the fluid travels further downstream in the bed of solid, it is enriched in those components that are only weakly retained by the solid. On the other hand, the components that are strongly retained by the solid are recovered by introducing into the solid bed an eluent stream to free them from the solid. Generally, the effectiveness of the separation is increased when the fluid and solid phases move countercurrently to each other. However, an effective and easy-to-operate system in which the solid phase is truly moved countercurrently to the fluid phase has not been developed. Instead, simulated moving bed contacting apparatuses have been used in which a simulation of the movement of the solid phase is carried out. In such a system, the points at which the feed and eluent streams are introduced into the solid bed and the points at which the enriched product streams are taken from the solid bed are moved sequentially and intermittently in the direction of the fluid flow. As the number of points of fluid introduction increases, the operation approaches more closely the continuous countercurrent moving bed. At the same time, the piping system becomes more complex, and the number of valves increases exponentially, resulting in a high cost. Therefore, effort has been expended to design a multiport rotary valve to replace all the valves in a simulated moving bed wherein an external fluid is introduced to various points in the solid bed by the rotation of some elements in the rotary valve so that a certain port communicates with an appropriate point in the solid bed. For example, U.S. Pat. No. 4,569,371 issued to Dolejs et al. discloses a complicated unitary axial multipart rotary valve which comprises a three-section cylindrical hollow stationary body and a cylindrical rotating body which fits inside the stationary body. The connections through which feed, eluent, and products are conducted to and from the simulated moving bed are made to the stationary body. Various channels are formed inside the rotating body and terminate in the circumferential surface of this rotating body such that different connections may be rendered communicable by the rotation of this rotating body. In order to ensure a successful operation, the bodies must be manufactured to a very high degree of precision. Even then, numerous sophisticated seals must be provided between the stationary and rotating bodies to prevent intermixing of the various fluid streams. As the rotating body becomes eroded with use, it can be imagined that a significant effort must be expended to repair the valve because of its complexity. Thus, such a valve incurs high investment and maintenance costs.
U.S. Pat. No. 5,676,826 issued to Rossiter and Riley disclosed a fluid-solid contacting apparatus employing a rotary valve to conduct fluid streams to and from the apparatus. The fluid-solid contacting apparatus of this invention comprises a plurality of chambers containing a solid, which chambers are installed on a rotating carousel. The valve of this invention comprises an annular stationary head and an annular rotating head. Conduits are formed inside the stationary head and terminated in two sets of openings on two surfaces of the stationary head. External fluids are supplied to the fluid-solid apparatus and product streams from the apparatus are taken away through the first set of openings on the circumferential surface of the stationary head. Fluid conduits from the entrance and exit ends of each chamber communicate with still other sections of conduits precisely arranged in the rotating head. Through a synchronous rotation of the rotating head and the carousel, the conduits in this head are aligned to the second set of openings on the stationary head, resulting in the appropriate connections between external fluid conduits and selected chambers. The number of conduits formed in the rotating head is very large because each chamber is provided with two conduits: one to its entrance and one to its exit end. Therefore, in order to ensure a perfect alignment between certain of such a large number of conduits in the rotating head and the second set of openings in the stationary head, the manufacturing of such a valve requires a very high degree of precision, thus incurring a high cost. In addition, the operation of this rotary valve requires the synchronous rotation of both the rotating head of the valve and the carousel of the chambers. As the scale of the operation and, thus, the size of each of the chambers, increases the operation becomes expensive or even impractical.
Therefore, it is an object of the present invention to provide an improved rotary valve for simultaneously directing a plurality of fluid streams into and out of a fluid-solid contacting apparatus employed for separating a multicomponent fluid mixture, which valve does not have the disadvantages of the prior-art valves. It is a further object of the present invention to provide a rotary valve that has fewer moving parts and a simpler construction than prior-art rotary valves. Other advantages of the present invention will become apparent upon a perusal of the instant disclosure.
Generally, the present invention provides a multiport rotary valve which has a stationary circular head which has at least one primary port for connection with a fluid stream and at least one secondary port. In practice, it is preferred to have a number of primary and secondary ports for connection with fluid separation equipment, for example.
The stationary head, which can comprises number of ports formed as a component assemble, includes one circular channel formed therein which is associated with a primary port and at least one second concentric circular channel associated with a secondary port or ports.
A rotatable head is provided having at least one radial chamber, the radial chamber includes first and second ports for connection with one of at least one first channels and one of the second ports.
The valve includes an indexable drive for rotating the rotatable head between pre-selected primary and secondary ports.
In an example of the invention, optionally, a sensor is used to control the position of the rotatable head relative to the first head.
In a presently preferred embodiment, a rotary valve is provided having multiple ports for connection with a plurality of external fluid-carrying conduits to direct fluid streams contained in these conduits, according to a pre-determined cycle, into and out of a fluid-solid contacting apparatus comprising a plurality of separation zones for a separation of a multicomponent fluid mixture. The rotary valve permits the connection of a fluid-carrying conduit to at most one other fluid-carrying conduit and prevents intermixing of fluids contained in the different fluid-carrying conduits while such fluids are flowing through the apparatus. After a predetermined time, one of any two interconnected fluid-carrying conduits is replaced by a different fluid-carrying conduit through a movement of an element of the rotary valve so that fluid is directed to or from a different position within the fluid-solid contacting apparatus. In the same manner, the rotary valve advances sequentially through its different positions or indices in accordance with the previously determined cycle.
A preferred embodiment of the rotary valve comprises a plurality of cooperative assemblies: a circular rotatable head having first and second opposed surfaces, and at least one stationary head assembly having first and second opposed surfaces. The rotatable and stationary head assemblies have circular shapes of substantially equal diameters. The rotatable head is disposed adjacently to one stationary surface of a stationary head assembly such that the centers of the assemblies substantially coincide, and rotates about an axis of rotation that runs perpendicularly to the circular surfaces of the assemblies and through their substantially coincident centers. The rotatable head assembly is urged against a stationary head assembly by a force that is supplied to the surface of the rotatable head opposite to a stationary head assembly.
A plurality of concentric circular channels is formed in the second stationary surface adjacent to the rotatable head. A plurality of primary connections is provided on the surface of a stationary head assembly opposite to the rotatable head assembly, through which primary connections fluid is conducted to or from the overall fluid-solid contacting apparatus. Each primary connection communicates with a cylindrical primary bore that runs through the thickness of the stationary head assembly on which these primary connections are disposed and terminates in one of the concentric circular channels of the same stationary head assembly. A plurality of secondary connections is uniformly spaced apart on a circle concentric with the circular channels and attached to the same or another stationary head assembly, and forms an array of connections to intermediate points representing the end of one and the beginning of another separation zone within the fluid-solid contacting apparatus. Each secondary connection communicates with a separate cylindrical secondary bore that runs through the thickness of the stationary head on which it is attached and that is in alignment with said secondary connection. The number of secondary connections is equal to the number of separation zones of the fluid-solid contacting apparatus so that each separation zone is connected to one secondary connection at an appropriate time.
A plurality of radial chambers are formed within the thickness of the rotating head assembly so to allow for the communication between the primary connections and each of the secondary connections. The number of radial chambers are equal to the number of concentric circular channels. Each radial chamber connects the cylindrical secondary bore that is in communication with a selected secondary connection to a cylindrical primary bore that is in communication with one of the primary connections through one of the circular channels, thereby allowing fluid present at a primary connection to be conducted to a separation zone or allowing fluid from another separation zone to be conducted to another primary connection. At a predetermined time, the rotating head assembly rotates and advances to the next position or index so that fluid is conducted to and from the next separation zones in the sequence. In this manner, each separation zone performs the separation of the fluid components for a defined time and is subsequently treated by an eluent so that the separation capability of the solid is recovered for further separation use for the same defined time.
The solid is often said to have been regenerated when its separation capability has been recovered to such a degree that it becomes useable to effect the separation when it is contacted again with the multicomponent fluid mixture. The rotation of the rotating head assembly can also be initiated when the concentration of a component of the fluid mixture coming from a separation zone reaches a predetermined level. The separation of the components of the fluid mixture is carried out continuously and indefinitely through the rotation of the rotating head assembly. Other advantages of the invention will become apparent from a perusal of the following detailed description of the presently preferred embodiment taken in connection with the accompanying drawings.